An integrated braking system is a technology of an integrated braking system that integrates ESC and an electric booster, and FIG. 1 illustrates an integrated braking system according to the related art.
The braking system illustrated in the drawing includes a hydraulic piston cylinder 2 that can be substantially moved by a brake pedal 1, a moving simulator device 3 that interacts with the hydraulic piston cylinder 2, a pressure medium storage 4 that is connected to the hydraulic piston cylinder 2, a pressure generating unit 5 that can be electrically controlled, a pressure control unit whose outlet ports are connected to wheels 8, 9, 10 and 11 of a vehicle (not illustrated), inlet and outlet valves 6a to 6d and 7a to 7d, and an electronic control and adjustment unit 12 that activates components that can be electrically controlled.
Pressure are applied to inlet ports of the inlet valves 6a to 6d through pressure lines I and II, and pressure sensors 22 and 23 are provided to measure pressures within the pressure lines I and II. Return lines 14a and 14b are provided at outlet ports of the outlet valves 7a to 7d. Further, the hydraulic piston cylinder 2 which is a moving unit of the braking system has two hydraulic pistons 15 and 16 within a housing 21, and the hydraulic pistons are provided in series. Pressure chambers 17 and 18 are provided together with the hydraulic pistons 15 and 16. The pressure chambers 17 and 18 may be connected to the pressure medium storage 4 through connection lines.
Meanwhile, the pressure chambers 17 and 18 are connected to the pressure lines I and II through hydraulic lines, and the pressure lines I and II are connected to the inlet ports of the inlet valves 6a to 6d or the pressure control unit. Shutoff valves 24a and 24b are respectively provided at the hydraulic lines. Furthermore, pressure sensors 25 are respectively provided at the hydraulic lines. Here, a piston rod 26 connected to the brake pedal 1 interacts with the first piston 15.
The pressure generating unit 5 is designed as a hydraulic cylinder piston or an electric hydraulic actuator, and a piston 33 may be operated by an electric motor through a rotational and translational motion. Meanwhile, the pressure generating unit 5 may include two hydraulic chambers 31 and 32 with the piston 33 interposed therebetween, and the two hydraulic chambers 31 and 32 are connected to the pressure lines I and II through hydraulic lines. Meanwhile, check valves 45 and 46 are provided at the hydraulic lines of the hydraulic chambers 31 and 32.
The above-stated braking system operates the shutoff valves 24a and 24b along with operation of the brake pedal 1 to shut off hydraulic connection between the brake pedal 1 and the wheels 8, 9, 10 and 11 and operates the motor to transmit hydraulic pressures through the hydraulic chambers 31 and 32. FIG. 1 illustrates the operation of the connection lines. A sky-blue line depicts movement of a pressure transmitted by the operation of the brake pedal 1 by a driver, a red line depicts movement to transmit a pressure to the wheels 8, 9, 10 and 11 by the operation of the motor, and a green line depicts movement to transmit a pressure to the wheels 8, 9, 10 and 11 by the hydraulic chamber 31.
Meanwhile, in the braking system, in general, when the shutoff valves 24a and 24b are closed, connection between the pressure medium storage 4 and the hydraulic chamber 32 of the pressure generating unit 5 is shut off. Accordingly, after the brake pedal 1 is released, in order to allow the hydraulic chamber 32 to be in an atmospheric pressure state by connecting the pressure medium storage 4 and the hydraulic chamber 32, the shutoff valves 24a and 24b are opened again. When the shutoff valves 24a and 24b are continuously closed, even though the piston 33 is returned, a residual pressure may be generated by oil introduced through the check valve 46. Accordingly, the braking system needs to constantly operate or stop the shutoff valves 24a and 24b depending on the operation of the brake pedal 1.
However, as mentioned above, when the shutoff valves 24a and 24b are operated whenever the brake pedal 1 is operated, plunger impact noise may be caused by frequent operation of the shutoff valves 24a and 24b. Furthermore, the number of operations of the shutoff valves 24a and 24b is increased, durability of the shutoff valves 24a and 24b may be degraded. Moreover, when the brake pedal 1 is quickly depressed, if operation responses of the shutoff valves 24a and 24b are slower than an application speed of the brake pedal 1, this may cause inconvenience in the brake pedal 1.
Accordingly, in order to solve the aforementioned problems, an applicant of the present invention has invented a braking system with more reliability.
[Patent Literature 1] International Patent Publication No. WO 2013/017037 (published on Feb. 9, 2012)